1. Field of the Invention
This invention relates to sample decomposing apparatus capable of rapidly decomposing or digesting the sample with easy operation by using microwave heating.
2. Description of the Prior Art
To analyze nitrogen component or metal components contained in such samples as coal, petroleum, heavy oil, fertilizer, soil, foodstuff, biological samples, etc., it is necessary to predecompose or digest the sample.
Prior art methods of decomposition include so-called Kjeldahl decomposition method in which such decomposition agent as sulfuric acid, potassium sulfate, copper sulfate and a decomposition catalyst is added to the sample and heated, and methods utilizing sulfuric acid and nitric acid; perchloric acid and nitric acid, respectively. However, these prior art methods are disadvantageous in that it takes a long time of 2 to 10 hours for decomposing the sample as desired.
To decrease the decomposition time, in recent years it has been proposed a method in which a flask containing a sample and a decomposing agent is disposed in a container heated by microwave. This method, however, has such defect that vapor or gas generated from the flask at the early stage of decomposition condenses on the inner wall of the heating container, and that where perchloric acid is used, a white fume of the perchloric acid fills the container, thus making it impossible to inspect the interior thereof. In the wet decomposition of a sample, incapability of inspecting the interior constitutes a fatal defect because foaming or bumping, that is, violent boiling often occurs unless the heating condition at the early heating stage is adequate.